FM 21-76 | Chapter 13 - Desert Survival

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CHAPTER 13 - DESERT SURVIVAL

To survive and evade in arid or desert areas, you must understand and prepare
for the environment you will face. You must determine your equipment needs,
the tactics you will use, and how the environment will affect you and your
tactics. Your survival will depend upon your knowledge of the terrain, basic
climatic elements, your ability to cope with these elements, and your will to
survive.

TERRAIN

Most arid areas have several types of terrain. The five basic desert terrain
types are--

Mountainous (High Altitude).

Rocky plateau.

Sand dunes.

Salt marshes.

Broken, dissected terrain ("gebel" or "wadi").

Desert terrain makes movement difficult and demanding. Land navigation will
be extremely difficult as there may be very few landmarks. Cover and concealment
may be very limited; therefore, the threat of exposure to the enemy remains
constant.

Mountain Deserts

Scattered ranges or areas of barren hills or mountains separated by dry, flat
basins characterize mountain deserts. High ground may rise gradually or abruptly
from flat areas to several thousand meters above sea level. Most of the
infrequent rainfall occurs on high ground and runs off rapidly in the form of
flash floods. These floodwaters erode deep gullies and ravines and deposit sand
and gravel around the edges of the basins. Water rapidly evaporates, leaving the
land as barren as before, although there may be short-lived vegetation. If
enough water enters the basin to compensate for the rate of evaporation, shallow
lakes may develop, such as the Great Salt Lake in Utah, or the Dead Sea. Most of
these lakes have a high salt content.

Rocky Plateau Deserts

Rocky plateau deserts have relatively slight relief interspersed with
extensive flat areas with quantities of solid or broken rock at or near the
surface. There may be steep-walled, eroded valleys, known as wadis in the Middle
East and arroyos or canyons in the United States and Mexico. Although their flat
bottoms may be superficially attractive as assembly areas, the narrower valleys
can be extremely dangerous to men and material due to flash flooding after
rains. The Golan Heights is an example of a rocky plateau desert.

Sandy or Dune Deserts

Sandy or dune deserts are extensive flat areas covered with sand or gravel.
"Flat" is a relative term, as some areas may contain sand dunes that
are over 300 meters high and 16 to 24 kilometers long. Trafficability in such
terrain will depend on the windward or leeward slope of the dunes and the
texture of the sand. Other areas, however, may be flat for 3,000 meters and
more. Plant life may vary from none to scrub over 2 meters high. Examples of
this type of desert include the edges of the Sahara, the empty quarter of the
Arabian Desert, areas of California and New Mexico, and the Kalahari in South
Africa.

Salt Marshes

Salt marshes are flat, desolate areas, sometimes studded with clumps of grass
but devoid of other vegetation. They occur in arid areas where rainwater has
collected, evaporated, and left large deposits of alkali salts and water with a
high salt concentration. The water is so salty it is undrinkable. A crust that
may be 2.5 to 30 centimeters thick forms over the saltwater.

In arid areas there are salt marshes hundreds of kilometers square. These
areas usually support many insects, most of which bite. Avoid salt marshes. This
type of terrain is highly corrosive to boots, clothing, and skin. A good example
is the Shat-el-Arab waterway along the Iran-Iraq border.

Broken Terrain

All arid areas contain broken or highly dissected terrain. Rainstorms that
erode soft sand and carve out canyons form this terrain. A wadi may range from 3
meters wide and 2 meters deep to several hundred meters wide and deep. The
direction it takes varies as much as its width and depth. It twists and turns
and forms a mazelike pattern. A wadi will give you good cover and concealment,
but do not try to move through it because it is very difficult terrain to
negotiate.

ENVIRONMENTAL FACTORS

Surviving and evading the enemy in an arid area depends on what you know and
how prepared you are for the environmental conditions you will face. Determine
what equipment you will need, the tactics you will use, and the environment's
impact on them and you.

In a desert area there are seven environmental factors that you must
consider--

Low rainfall.

Intense sunlight and heat.

Wide temperature range.

Sparse vegetation.

High mineral content near ground surface.

Sandstorms.

Mirages.

Low Rainfall

Low rainfall is the most obvious environmental factor in an arid area. Some
desert areas receive less than 10 centimeters of rain annually, and this rain
comes in brief torrents that quickly run off the ground surface. You cannot
survive long without water in high desert temperatures. In a desert survival
situation, you must first consider "How much water do I have?" and
"Where are other water sources?"

Intense Sunlight and Heat

Intense sunlight and heat are present in all arid areas. Air temperature can
rise as high as 60 degrees C (140 degrees F) during the day. Heat gain results
from direct sunlight, hot blowing winds, reflective heat (the sun's rays
bouncing off the sand), and conductive heat from direct contact with the desert
sand and rock (Figure 13-1).

The temperature of desert sand and rock averages 16 to 22 degrees C (30 to 40
degrees F) more than that of the air. For instance, when the air temperature is
43 degrees C (110 degrees F), the sand temperature may be 60 degrees C (140
degrees F).

Intense sunlight and heat increase the body's need for water. To conserve
your body fluids and energy, you will need a shelter to reduce your exposure to
the heat of the day. Travel at night to lessen your use of water.

Radios and sensitive items of equipment exposed to direct intense sunlight
will malfunction.

Wide Temperature Range

Temperatures in arid areas may get as high as 55 degrees C during the day and
as low as 10 degrees C during the night. The drop in temperature at night occurs
rapidly and will chill a person who lacks warm clothing and is unable to move
about. The cool evenings and nights are the best times to work or travel. If
your plan is to rest at night, you will find a wool sweater, long underwear, and
a wool stocking cap extremely helpful.

Sparse Vegetation

Vegetation is sparse in arid areas. You will therefore have trouble finding
shelter and camouflaging your movements. During daylight hours large areas of
terrain are visible and easily controlled by a small opposing force.

If traveling in hostile territory, follow the principles of desert
camouflage--

Hide or seek shelter in dry washes (wadis) with thicker growths of
vegetation and cover from oblique observation.

Use the shadows cast from brush, rocks, or outcropping. The temperature in
shaded areas will be 11 to 17 degrees C cooler than the air temperature.

Cover objects that will reflect the light from the sun.

Before moving, survey the area for sites that provide cover and concealment.
You will have trouble estimating distance. The emptiness of desert terrain
causes most people to underestimate distance by a factor of three: What appears
to be 1 kilometer away is really 3 kilometers away.

High Mineral Content

All arid regions have areas where the surface soil has a high mineral content
(borax, salt, alkali, and lime). Material in contact with this soil wears out
quickly, and water in these areas is extremely hard and undrinkable. Wetting
your uniform in such water to cool off may cause a skin rash. The Great Salt
Lake area in Utah is an example of this type of mineral-laden water and soil.
There is little or no plant life; there-fore, shelter is hard to find. Avoid
these areas if possible.

Sandstorms

Sandstorms (sand-laden winds) occur frequently in most deserts. The "Seistan"
desert wind in Iran and Afghanistan blows constantly for up to 120 days. Within
Saudi Arabia, winds average 3.2 to 4.8 kilometers per hour (kph) and can reach
112 to 128 kph in early afternoon. Expect major sandstorms and dust storms at
least once a week.

The greatest danger is getting lost in a swirling wall of sand. Wear goggles
and cover your mouth and nose with cloth. If natural shelter is unavailable,
mark your direction of travel, lie down, and sit out the storm.

Dust and wind-blown sand interfere with radio transmissions. Therefore, be
ready to use other means for signaling, such as pyrotechnics, signal mirrors, or
marker panels, if available.

Mirages

Mirages are optical phenomena caused by the refraction of light through
heated air rising from a sandy or stony surface. They occur in the interior of
the desert about 10 kilometers from the coast. They make objects that are 1.5
kilometers or more away appear to move.

This mirage effect makes it difficult for you to identify an object from a
distance. It also blurs distant range contours so much that you feel surrounded
by a sheet of water from which elevations stand out as "islands."

The mirage effect makes it hard for a person to identify targets, estimate
range, and see objects clearly. However, if you can get to high ground (3 meters
or more above the desert floor), you can get above the superheated air close to
the ground and overcome the mirage effect. Mirages make land navigation
difficult because they obscure natural features. You can survey the area at
dawn, dusk, or by moonlight when there is little likelihood of mirage.

Light levels in desert areas are more intense than in other geographic areas.
Moonlit nights are usually crystal clear, winds die down, haze and glare
disappear, and visibility is excellent. You can see lights, red flash-lights,
and blackout lights at great distances. Sound carries very far.

Conversely, during nights with little moonlight, visibility is extremely
poor. Traveling is extremely hazardous. You must avoid getting lost, falling
into ravines, or stumbling into enemy positions. Movement during such a night is
practical only if you have a compass and have spent the day in a shelter,
resting, observing and memorizing the terrain, and selecting your route.

NEED FOR WATER

The subject of man and water in the desert has generated considerable
interest and confusion since the early days of World War II when the U. S. Army
was preparing to fight in North Africa. At one time the U. S. Army thought it
could condition men to do with less water by progressively reducing their water
supplies during training. They called it water discipline. It caused hundreds of
heat casualties.

A key factor in desert survival is understanding the relationship between
physical activity, air temperature, and water consumption. The body requires a
certain amount of water for a certain level of activity at a certain
temperature. For example, a person performing hard work in the sun at 43 degrees
C requires 19 liters of water daily. Lack of the required amount of water causes
a rapid decline in an individual's ability to make decisions and to perform
tasks efficiently.

Your body's normal temperature is 36.9 degrees C (98.6 degrees F). Your body
gets rid of excess heat (cools off) by sweating. The warmer your body
becomes--whether caused by work, exercise, or air temperature--the more you
sweat. The more you sweat, the more moisture you lose. Sweating is the principal
cause of water loss. If a person stops sweating during periods of high air
temperature and heavy work or exercise, he will quickly develop heat stroke.
This is an emergency that requires immediate medical attention.

Figure 13-2 shows daily water requirements for various
levels of work. Understanding how the air temperature and your physical activity
affect your water requirements allows you to take measures to get the most from
your water supply. These measures are--

Find shade! Get out of the sun!

Place something between you and the hot ground.

Limit your movements!

Conserve your sweat. Wear your complete uniform to include T-shirt. Roll
the sleeves down, cover your head, and protect your neck with a scarf or
similar item. These steps will protect your body from hot-blowing winds and
the direct rays of the sun. Your clothing will absorb your sweat, keeping it
against your skin so that you gain its full cooling effect. By staying in
the shade quietly, fully clothed, not talking, keeping your mouth closed,
and breathing through your nose, your water requirement for survival drops
dramatically.

If water is scarce, do not eat. Food requires water for digestion;
therefore, eating food will use water that you need for cooling.

Thirst is not a reliable guide for your need for water. A person who uses
thirst as a guide will drink only two-thirds of his daily water requirement. To
prevent this "voluntary" dehydration, use the following guide:

At temperatures below 38 degrees C, drink 0.5 liter of water every hour.

At temperatures above 38 degrees C, drink 1 liter of water every hour.

Drinking water at regular intervals helps your body remain cool and decreases
sweating. Even when your water supply is low, sipping water constantly will keep
your body cooler and reduce water loss through sweating. Conserve your fluids by
reducing activity during the heat of day. Do not ration your water! If
you try to ration water, you stand a good chance of becoming a heat casualty.

HEAT CASUALTIES

Your chances of becoming a heat casualty as a survivor are great, due to
injury, stress, and lack of critical items of equipment. Following are the major
types of heat casualties and their treatment when little
water and no medical help are available.

Heat Cramps

The loss of salt due to excessive sweating causes heat cramps. Symptoms are
moderate to severe muscle cramps in legs, arms, or abdomen. These symptoms may
start as a mild muscular discomfort. You should now stop all activity, get in
the shade, and drink water. If you fail to recognize the early symptoms and
continue your physical activity, you will have severe muscle cramps and pain.
Treat as for heat exhaustion, below.

Heat Exhaustion

A large loss of body water and salt causes heat exhaustion. Symptoms are
headache, mental confusion, irritability, excessive sweating, weakness,
dizziness, cramps, and pale, moist, cold (clammy) skin. Immediately get the
patient under shade. Make him lie on a stretcher or similar item about 45
centimeters off the ground. Loosen his clothing. Sprinkle him with water and fan
him. Have him drink small amounts of water every 3 minutes. Ensure he stays
quiet and rests.

Heat Stroke

A severe heat injury caused by extreme loss of water and salt and the body's
inability to cool itself. The patient may die if not cooled immediately.
Symptoms are the lack of sweat, hot and dry skin, headache, dizziness, fast
pulse, nausea and vomiting, and mental confusion leading to unconsciousness.
Immediately get the person to shade. Lay him on a stretcher or similar item
about 45 centimeters off the ground. Loosen his clothing. Pour water on him (it
does not matter if the water is polluted or brackish) and fan him. Massage his
arms, legs, and body. If he regains consciousness, let him drink small amounts
of water every 3 minutes.

PRECAUTIONS

In a desert survival and evasion situation, it is unlikely that you will have
a medic or medical supplies with you to treat heat injuries. Therefore, take
extra care to avoid heat injuries. Rest during the day. Work during the cool
evenings and nights. Use a buddy system to watch for heat injury, and observe
the following guidelines:

Make sure you tell someone where you are going and when you will return.

Watch for signs of heat injury. If someone complains of tiredness or
wanders away from the group, he may be a heat casualty.

Drink water at least once an hour.

Get in the shade when resting; do not lie directly on the ground.

Do not take off your shirt and work during the day.

Check the color of your urine. A light color means you are drinking enough
water, a dark color means you need to drink more.

DESERT HAZARDS

There are several hazards unique to desert survival. These include insects,
snakes, thorned plants and cacti, contaminated water, sunburn, eye irritation,
and climatic stress.

Insects of almost every type abound in the desert. Man, as a source of water
and food, attracts lice, mites, wasps, and flies. They are extremely unpleasant
and may carry diseases. Old buildings, ruins, and caves are favorite habitats of
spiders, scorpions, centipedes, lice, and mites. These areas provide protection
from the elements and also attract other wild-life. Therefore, take extra care
when staying in these areas. Wear gloves at all times in the desert. Do not
place your hands anywhere without first looking to see what is there. Visually
inspect an area before sitting or lying down. When you get up, shake out and
inspect your boots and clothing. All desert areas have snakes. They inhabit
ruins, native villages, garbage dumps, caves, and natural rock outcropping that
offer shade. Never go barefoot or walk through these areas without carefully
inspecting them for snakes. Pay attention to where you place your feet and
hands. Most snakebites result from stepping on or handling snakes. Avoid them.
Once you see a snake, give it a wide berth.